Department of Hematology, Tangdu Hospital, Fourth Military Medical University, Xi'an 710038, China.
Mol Cell Biochem. 2010 Jul;340(1-2):7-14. doi: 10.1007/s11010-010-0394-9. Epub 2010 Feb 16.
The Notch signaling pathway has been implicated in the development of several leukemia and lymphoma. In order to investigate the relationship between Notch signaling and acute myeloid leukemia (AML), in this study, we expressed a recombinant Notch ligand protein, the DSL domain of the human Jagged1 fused with GST (GST-Jag1). GST-Jag1 could activate Notch signaling in the human promyelocytic leukemia cell line HL60, as shown by a reporter assay and the induced expression of Notch effector gene Hes1 and Hes5. However, GST-Jag1 had no effect on the proliferation and survival of HL60 cells. HL60 cells expressed both Notch ligands and receptors, and had a potential of reciprocal stimulation of Notch signaling between cells. We, therefore, blocked Notch signaling in cultured HL60 cells using a gamma-secretase inhibitor (GSI). We found that GSI inhibited the proliferation of HL60 cells significantly by blocking the cell-cycle progression in the G1 phase. Furthermore, GSI induced remarkably apoptosis of HL60 cells. These changes in GSI-treated HL60 cells correlated with the down-regulation of c-Myc and Bcl2, and the low phosphorylation of the Rb protein. These results suggested that reciprocal Notch signaling might be necessary for the proliferation and survival of AML cells, possibly through the maintenance of the expression of c-Myc and Bcl2, as well as the phosphorylation of the Rb protein.
Notch 信号通路与几种白血病和淋巴瘤的发生有关。为了研究 Notch 信号与急性髓系白血病（AML）之间的关系，在本研究中，我们表达了一种重组 Notch 配体蛋白，即与人 Jagged1 的 DSL 结构域融合的 GST（GST-Jag1）。GST-Jag1 可通过报告基因检测和 Notch 效应基因 Hes1 和 Hes5 的诱导表达激活 HL60 人早幼粒细胞白血病细胞系中的 Notch 信号。然而，GST-Jag1 对 HL60 细胞的增殖和存活没有影响。HL60 细胞表达 Notch 配体和受体，并且具有细胞间 Notch 信号相互刺激的潜力。因此，我们使用γ-分泌酶抑制剂（GSI）阻断培养的 HL60 细胞中的 Notch 信号。我们发现 GSI 通过阻断 G1 期的细胞周期进程显著抑制 HL60 细胞的增殖。此外，GSI 诱导 HL60 细胞明显凋亡。GSI 处理的 HL60 细胞中的这些变化与 c-Myc 和 Bcl2 的下调以及 Rb 蛋白的低磷酸化有关。这些结果表明，相互 Notch 信号可能是 AML 细胞增殖和存活所必需的，可能通过维持 c-Myc 和 Bcl2 的表达以及 Rb 蛋白的磷酸化来实现。
